The dashed blue line in Fig. REF b shows the \(Q\) -factor obtained from Fano fit on the reflectivity curve obtained from the full vectorial simulations (calculated as \(Q=\lambda /\gamma \) ).
This is in excellent agreement with the eigenmode analysis results, meaning that the two methods are consistent and reliable.
We observe that the Fano parameter, \(q\) , is always negative except in proximity of \(\alpha ^*\) , meaning that in the latter situation the quasi-BIC and the continuum phases are shifted by almost \(\pi /2\)[1]}.
